In the production of natural gas from gas wells, the gas frequently contains solid contaminants such as sand, pipe scale and other debris. The producing gas also frequently contains liquid contaminants such as water and petroleum products, namely distillate and various grades of crude oil. Gas flow measurement systems have been in use for many years, which function according to various conventional gas flow measurement formulae for accurate measurement of gas flow from the well. Typically, it is necessary to identify the volume of gas flowing from each particular well of a gas field to thus identify the volume of gas being conducted from the gas field to a gas handling system such as a gas transmission pipeline. More recently, various electronic gas flow measurement systems have been developed which incorporate microcomputers that provide gas flow calculations in accordance with gas temperature, pressure, differential pressure, etc. These electronic gas flow measurement systems are quite accurate and represent a substantial improvement over mechanical gas flow measurement devices. Most electronic and mechanical gas flow measurement systems also incorporate chart recorders with flow responsive pens which cause the volume of flow to be represented by ink lines on the charts. In most cases, the charts are of circular form and chart paper is changed out after each revolution of the rotary chart has occurred. These charts are utilized as visual indications of the volume of gas being sold to purchasers.
Regardless of the type of chart employed, it is well known that the conditions of gas flow from a producing gas well frequently have significant fluctuation, thereby causing rapid cycling of the ink pen of a chart recorder, resulting in a broad ink band on the chart which is defined by the amplitude of ink pen fluctuation responsive to fluctuation of the flowing gas. These broad ink bands require significant interpretation in order to establish accuracy of the flow conditions represented by the ink lines on the chart. In many cases, the fluctuations are sufficiently wide that a wide ink band on the chart renders it virtually useless for interpretation of gas flow. Similarly, wide fluctuations detected by the measurement equipment complicate the electronic recording procedure and, in some cases, there is a wide disparity between the gas flow information physically shown on the chart and the gas flow information represented by the electronic measurement equipment.
Fluctuations in gas flow from producing gas wells is caused by changes in the pressure of the natural gas being produced from the gas formation and it is also influenced by contaminants contained within the flowing gas. Further, the accuracy of flow measurement equipment is, in many cases, significantly influenced by contaminants contained in the flowing gas and by fluctuations in gas flow. For example, water produced with the gas builds up on the orifice of an orifice fitting and introduces flow anomalies developing inaccuracy in measurement as well as inducing fluctuations across the orifice which are picked up and displayed by the metering and recording equipment. In absence of water, the gas flow will be stable and otherwise easily measured. It is highly desirable, therefore, to ensure that gas flow from a producing gas well into gas flow measurement equipment have minimal rapid fluctuations so that the volume of gas flow as well as other gas flow conditions will be represented on the chart by a thin ink line which can be accurately interpreted. Further, it is highly desirable to ensure that natural gas flowing through gas flow measurement equipment be substantially free of liquid and solid contaminants to thereby enhance the accuracy of gas flow measurement.